Sang Gil is a homicide detective whose well deserved promotion is rewarded to another one of his colleges. On yet another typical day in the field, he’s assigned a simple suicide case with a rookie female detective, Eun Yeong, as his partner. Sang Gil grudgingly starts the investigation, but the case turns out to be much more complicated as it seemed. Blinded by the chance to earn a long overdue promotion, Sang Gil continues to investigate on his own without reporting to his superiors. Meanwhile, Eun Yeong questions the odd bite mark on the victim’s body, but Sang Gil ignores her discovery and continues on. But when a random wild animal attack kills another person, Eun Yeong senses a connection between the two deaths. Without realizing the seriousness of the situation, Sang Gil stubbornly continues to investigate the case alone, and Eun Yeong reluctantly follows along. When the two discover that the bite marks on the bodies belong to the same wolfdog (a crossbreed between a dog and a wolf), they begin to realize that all the victims are strangely connected to one another.